<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <link rel="stylesheet" href="./size.css">
    <style>
        .clearfix {
            width: 200px;
            /* height: 200px; */
            background-color: darkgrey;
        }

        .fl,
        .fr {
            width: 50px;
            height: 50px;
            background-color: #011f2f;
            color: #fff;
        }
    </style>
</head>

<body>
    <div class="clearfix">
        <div class="fl"></div>
        <div class="fr"></div>
    </div>
</body>

</html>